Health care experts have been informed of a US man contracting HIV despite being on PrEP. He’s thought to be the first man in California – and only the third in the US – to contract HIV while adhering to a daily PrEP regime.

PrEP is a medication that minimizes the chances of someone acquiring HIV, even if they do not use condoms.

News of the case was presented at the annual IDWeek conference in San Francisco, which concluded over the weekend. The conference is run by the Infectious Diseases Society of America.

The man was HIV negative when he began taking PrEP in San Francisco in late 2016. He continued to diagnose HIV negative when testing at three, six and ten months. Blood tests also demonstrated he continued to take his medication consistently.

HIV positive after being on PrEP for a year

After just over a year on PrEP, he received an HIV positive diagnosis in early 2018. He was immediately placed on HIV drugs and has maintained a suppressed viral load since that time.

Doctors were able to accurately diagnose the exact strain of HIV he picked up. It’s one identified with people who have taken HIV medication in the past but no longer take it. It was then revealed that the patient’s main male partner was HIV positive but no longer taking medication.

The partner was tested and found to have a high viral load of the resistant strain. He has resumed taking medication.

Researchers say it was the fact the patient came into contact with a resistant strain that led to him acquiring the virus. They believe he stuck to his PrEP regime well. They could tell this from analyzing his hair, which he happened to grow long.

Dr. Robert Grant, of the University of California San Francisco, said, ‘[The patient’s] long hair allowed us to test by centimeters, which allowed us to go back and read drug levels from six months ago.’

Previous cases of men becoming HIV positive while on PrEP

There have been five previous reports on men acquiring HIV while on Pre-Exposure Prophylaxis (PrEP). The first two occurred in Toronto and New York in 2016. In 2017, there were three more cases. One involved a man in North Carolina, one in Australia, and a fifth a man in Amsterdam.

The first four cases are believed to be due to the person on PrEP having sex with someone with a high viral load of a rare, resistant strain of HIV.

The fifth case is not believed to be linked to a drug-resistant strain of HIV. The Amsterdam man had an ‘unusually high number’ of sexual partners – averaging 50-70 a month – and several other sexual infections. Researchers have speculated he may have repeatedly exposed himself to HIV, which took a hold in his body after a slight dip in Truvada levels.

‘Greater than 99% effective’​Health experts say despite these rare cases, PrEP remains highly effective. The medication is taken by more than 350,000 people worldwide.

Dr. Grant said, ‘We know PrEP is greater than 99% effective. There are some cases where HIV will break through. We only have a handful of cases now, and next year, we’ll probably have a handful more. Fortunately, these cases are caught early, treated, and suppressed quickly. The person goes from taking one pill a day to one pill a day. The biggest difference is the stigma.’

Matthew Hodson, Chief Executive of HIV information organization NAM, agrees. 'We estimate that PrEP is more than 99% effective at preventing HIV. By comparison, a recent meta-analysis of the efficacy of condoms found that they prevented nine out of ten cases, this was a better result than previous analyses.

He said that in the UK, 93% of people diagnosed with HIV have suppressed the virus to a point where it cannot be passed on ‘in any circumstance.’ This is regardless of whether it’s a drug-resistant strain or not.

‘It’s vital to acknowledge that PrEP, just like other safer sex strategies isn’t 100% effective. It is also vital not to let isolated cases obscure how effective it is. PrEP has played a significant role in bringing down new HIV infections in London, Sydney, New York, San Francisco and other cities around the world.’